I am quite amazed by its sharpness. It took me some time to get used to the macro feature. I feel that 100mm would be lot easy if you are shooting insects. I find it very difficult to focus on the moving subjects with macro feature. Here is a shot that i am satisfied

Sharpness

Focusing

Pentax SMC P-D FA 50mm f/2.8 Macro Lens Review

Gary Wolstenholme reviews the lightweight Pentax SMC Pentax-D FA 50mm Macro f/2.8 lens.

Outstanding sharpness; Relatively lightweight; Decent build quality; Good value

No focus limiter; Manual focus ring is loose without clamp and feels gritty with it engaged; Hyperfocal scale is of limited use

Pentax SMC D-FA Macro 50mm F2.8 Review

Pentax's foray into full-frame digital is relatively recent, but it kept a few lenses from the film era in production to match with the digital K-1. One of those is the Pentax SMC D-FA Macro 50mm F2.8 ($299.95), which delivers strong optical performance, even if its fit and finish aren't on the same level as more modern lenses. It doesn't have the weather sealing, focus limiter, or internal motor that we're used to seeing on newer glass. But you can't argue with its image quality or its price, so we recommend it to Pentax shooters searching for a macro lens. Design The Macro 50mm ($316.95 at B&H Photo Video) is small and light, coming in at just 2.6 by 2.6 inches (HD) and 9.3 ounces. Its front element is also small, offering support for the 49mm filter size. The lens does telescope as it focuses close, however, which is a departure from modern macros with internal focus designs. The extension makes it feel a bit more fragile than it should, but using the included lens hood will pr...

The Pentax SMC D-FA Macro 50mm F2.8 lens delivers strong image quality and full-size macro magnification.

Quite sharp; 1:1 macro magnification; Focus clamp; No distortion; Aperture ring for film use; Compact

Screw-drive focus system; Telescopes when focused close; Omits focus limiter; No weather sealing